Vulcanizing rubber with 1-thiazolyl unsymmetrical-1, 4-piperazines



United rates Patent 9 F The present invention relates to new chemicalproducts as well as to means of obtaining such products and to the useof said products as accelerators of the vulcanization of rubber. Moreparticularly, the invention relates to newunsymmetrical-1,4-substitutedpiperazines containing in one position a thiazolylmercapto radical andin the other position an aryl, alkyl or aralkyl radical, and to the useas disclosed of such products.

The preferred class of compounds most conveniently may be represented bythe general formula wherein T represents a thiazolyl group, R representsalkyl, aryl, aralkyl, and alkoxy or halogen substituted derivativesthereof, and X, X X X X X X and X represent hydrogen or lower alkyl, atleast four being hydrogen.

These compounds may be obtained by oxidative condensation of a monoN-substituted piperazine and a mercaptothiazole. The requiredpiperazines are for the most part known compounds and in any case arederivable by known procedures. Examples of the new compounds comprise:

1-(Z-benzothiazolylrnercapto)-4-phenyl-2-methylpiperazine,

1-(2-benzothiazolylmercapto) -4phenyl-2,5-dimethylpiperazine,

1-(Z-benzothiazolylmercapto)-4-phenyl-2,3-dimethy1- piperazine,

1-(2benzothiazolylmercapto)-4-methy1-2,3-diethylpiperazine,

1-(2-benzothiazolylmercapto) -4-ethyl-2,2-dimethylpiperazine,

1-(2-benzothiazolylmercapto) -4-phenyl-2-ethylpiperazine,

1-(2-benzothiazolylmercapto)-4-methyl-2,2,3-trimethylpiperazme,

-1- (2-benzothiazolylmercapto) -4-methyl-2,2-dimethyl-3- ice 1-Z-benzothiazolylmercapto) -4-pmethoxybenzylpiperazine,

1-(2-benzothiazolylmercapto)-4-octylpiperazine,

1- (2-benzothiazolylmercapto) -4-dodecylpiperazine,

1-(2-benzothiazo1yhnercapto) -4-o-tolylpiperazine,

1-(Z-benzothiazolylmercapto)-4-b et a-n aphthylpip erazine,

1- (2b enzothiazolylmerc apto -4-alpha-naphthylpip erazine,

1- 2-b enzothiazolylmercapto) -4-p-bromophenylpip erazine,

1- (2-b enzothiazolylmercapto) 4-o-methoxyphenylpiperazine and 1- (2-benzothiazolylmercapto) -4-p-methoxyphenylpip erazine.

It is understood and is quite apparent that in place of2-benzothiazolylmercapto, other thiazolylmercapto radicals may besubstituted, as for example substituted derivatives where thesubstituents comprise nitro, phenyl, lower alkoxy and lower alkylradicals.

The preparation of the new compounds will be understood from the typicalexamples that follow.

EXAMPLE l.--PRODUCT A 1-(Z-Benzothiazolylmercapto)-4-Phenylpiperazine Asolution was prepared containing 13.9% by Weight of2-mercapt0benzothiazole in the form of the sodium salt thereof. To 300parts of this solution (0.25 mole of MBT) there were slowly added 61parts (0.375 mole) of N-phenylpiperazine while maintaining thetemperature of the mass between 20-25 C. and while agitating constantly.Thereupon 59 parts (0.15 mole) of 25% sulfuric acid were slowly addedWhile maintaining the temperature at the limits stated. There were thenslowly added at 4550 C. 22.35 parts (0.30 mole) of sodium hypochloritein the form of 155 ml. of solution containing 14.47 parts hypochloriteper ml. After the addition of all the hypochlorite, the temperature wasmaintained at 45-50" C. while agitating for approximately an hour.Unreacted oxidizing agent was then destroyed by the ad dition ofapproximately 2 parts of sodium sulfite and the mass then cooled toabout 25 C. by the addition of water. The insoluble product wasthereupon collected by filtration, Washed with water until the washingswere neutral in reaction and air-dried at 50 C. The product, M.P.163-165 C. after recrystallization from ethyl acetate, was obtained in99% yield. The product was soluble in acetone and chloroform, slightlysoluble in benzene and ethyl acetate and insoluble in water, ether,ethanol and heptane. Identification of the product as that expected andnamed above, namely C1'7H17N3S2, was confirmed by analysis whichproduced as results:

- Percent Percent Theory Found nitrogen 12. 83 13. 05 sulfur 19. 58 19.43

EXAMPLE 2.-PRODUCT B taining 40 parts (0.25 mole) of 25% sodiumhydroxide solution. The solution was clarified by filtration and wasthen employed with the other reactants in the manner already describedin detail. The yield obtained was Percent Percent;

Theory Found nitrogen 11. 61 11.57 sulfur 17. 72 17. 72

EXAMPLE 3.-PRODUCT C 1-(4,5-Dimethyl-Z-Tlziazolylmercapto)-4-Phenylpiperazine As another example of the invention, a solution wasprepared containing 36.2 parts (0.25 mole) of4,5-dimethyl-2-thiazolethiol dissolved in 50 parts of water containing40 parts (0.25 mole) of 25% sodium hydroxide solution. Proceeding againwith the same quantities of N-phenylpiperazine, acid, hypochlorite, andsodium sulfite as set forth in Example 1 hereof, the same procedure wasfollowed except that the addition of hypochlorite and agitationtherewith proceeded at a temperature of 2530 C. and instead of obtaininga solid product at the completion of the reaction, the entire mass wascooled and treated with ether, the ether extract was separated, washedwith water until the wash water was neutral to litmus and the ether wasremoved in vacuo. An amber colored semi-solid product was obtained whichwas insoluble in water but soluble in the common organic solvents.

EXAMPLE 4.PRODUCT D 1 -(2-Benzoth iazolylm ercapto) -4-BenzylpiperazineA solution was prepared by mixing 43 parts (0.25 mole) of 97%mercaptobenzothiazole, 25 parts of Water and 40 parts (0.25 mole) of 25%aqueous sodium hydroxide. The solution was stirred while adding to it110 parts (0.625 mole) of N-benzylpiperazine and then stirred for about15 minutes. Over a period of about 15 minutes 49.5 parts by weight of25% sulfuric acid was added and the solution stirred for another 15minutes. Then 0.3 mole of sodium hypochlorite in the form of an aqueoussolution containing 16.1 grams NaOCl per 100 ml. was added at 45-50 C.over a period of one and one-half hours. The stirred reaction mixturewas held at 45-50 C. for one hour longer and 4 parts of sodium sulfiteadded after cooling to 25 C. The stirred reaction mixture was extractedwith ethyl ether, the ether extracts washed with water and dried. Afterremoving the ether in vacuo a solid remained which was air-dried on aporous plate at 25-30 C. The product after recrystallizing from ethylalcohol melted at 6163 C. It contained 12.0% nitrogen and 18.2% sulfurcompared to 12.3% nitrogen and 18.8% sulfur calculated for C H N S Theaction as rubber vulcanization accelerators of the sulfenarnides of thetype set forth in the foregoing examples are described in the followingtypical results wherein a rubber-black tread formulation was employed.The rubber stocks were obtained in the Well'known manner from thefollowing recipes inwhich parts by weight are indicated:

Smoked sheets rubber 100.0 Carbon black (Philblack 50.0 Zinc oxide 5.0Stearic acid 2.0 Saturated hydrocarbon softener 3.0 Sulfur 2.5

To the above there were added in separate stocks Product A Product BProduct 0 Vulcanization was completed at a temperature of 144 C. and thefollowing results obtained on the stocks:

Modulus of elasticity at 300% elongation 2, 030 1, 803 2, 036 Tensilestrength at break 3, 730 3, 270 3, 616 Mooney scorch at; 121 0 21 21 Theresults indicate that the products of the present invention displayactivity as vulcanization accelerators typical of the class ofsulfenamide products. The products themselves, as was shown in theexamples, are easy to prepare, are relatively economical to obtain,possess good physical properties and also were found to exhibit goodhandling properties in rubber stocks and to show good stability on longcontinued storage.

It is intended to cover all changes and modifications of the examples ofthe invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

What is claimed is:

1. The process of vulcanizing a sulfur vulcanizable rubber whichcomprises heating at vulcanizing temperature rubber and sulfur in thepresence of a small quantity suflicient to accelerate vulcanization of aproduct having the structure wherein T is a thiazolyl radical selectedfrom the group consisting of di(lower alkyl) substituted thiazolyl,benzothiazolyl and nitro-, chloro-, phenyl-, lower alkoxyand loweralkyl-substituted benzothiazolyl, R is selected from the groupconsisting of alkyl of 1-12 carbon atoms, aryl and aryl substitutedlower alkyl, the aryl radicals being selected from the group consistingof phenyl, tolyl, naphthyl, lower alkoxy substituted phenyl, chlorinesubstituted phenyl and bromine substituted phenyl and X, X X X X X X andX are selected from the group consisting of hydrogen and lower alkyl atleast four of X, X X X X X X and X being 5 hydrogen.

2. The process of vulcanizing a sulfur vulcanizable rubber whichcomprises heating at vulcanizing temperature rubber and sulfur in thepresence of a small quantity suflicient to accelerate vulcanization of aproduct having the structure wherein T represents benzothiazolyl and Rrepresents a lower alkyl radical.

3. The process of vulcanizing a sulfur vulcanizable rubber whichcomprises heating at vulcanizing temperature rubber and sulfur in thepresence of 1-(2-benzothiazolylmercapto)-4-phenylpiperazine.

4. The process of vulcanizing a sulfur vulcanizable rubber whichcomprises heating at vulcanizing temperature rubber and sulfur in thepresence of l-(4,5-dimethyl- 2-thiazolylmercapto)-4-phenylpiperazine.

5. The process of vulcanizing a sulfur vulcanizable rubber whichcomprises heating at vulcanizing temperature rubber and sulfur in thepresence of 1-(5-chloro-2- benzothiazolylmercapto)-4 phenylpiperazine.

6. The process of vulcanizing a sulfur vulcanizable rubber whichcomprises heating at 'vulcanizing temperature rubber and sulfur in frhepresence of 1-(2-benzothiazolylmercapto)-4 benzy1piperazine.

References Cited in the file of this patent UNITED STATES PATENTS Joneset a1. May 26, 1942 Emerson et a1. Aug. 7, 1951 DAmico Oct. 1, 1957DAmico et a1. Sept. 23, 1958

1. THE PROCESS OF VULCANIZING A SULFUR VULCANIZABLE RUBBER WHICHCOMPRISES HEATING AT VULCANIZING TEMPERATURE RUBBER AND SULFUR IN THEPRESENCE OF A SMALL QUANTITY SUFFICIENT TO ACCELERATE VULCANIZATION OF APRODUCT HAVING THE STRUCTURE